1. Field of the Invention
The present invention relates to a recording/reproducing apparatus of an optical card. In the specification, a recording/reproducing apparatus incorporates: an apparatus for recording (or writing) information or data to an optical card; an apparatus for playing back (or reading) information or data from an optical card; and an apparatus for executing both of the recording and reading operations. On the other hand, an optical card incorporates not only an optical card to/from which information or data can be optically recorded/reproduced but also an optical card to/from which information or data can be magneto optically recorded/reproduced.
2. Description of the Related Art
FIG. 19 shows a whole optical card and an enlarged part thereof.
A number of information recorded or recording tracks 17 which are specified by track guides 18 are provided in an information recording portion 16 of an optical card 1. Bits indicative of information are recorded in a form of pits 19 onto the tracks 17 (in the case of the optically recordable/reproducible card). The track guides 18 are provided for allowing an optical head for recording/reproducing to follow the tracks (what is called a tracking control).
In the optical card in the embodiment, information is optically written/read. In the recording mode, the pits 19 are formed by causing a thermal irreversible change by a light irradiation in the information recording portion 16. On the contrary, in the reproducing mode, the light is irradiated to the pits 19 and regions around them and the reflected lights are received, thereby detecting the presence or absence of the pits. In the case of the embodiment, light reflectances at the pits 19 and track guides 18 are lower than those of the regions around them.
FIGS. 20 to 22 show an example of a mechanical construction of the recording/reproducing apparatus of an optical card. Such a recording/reproducing apparatus has been disclosed in, for instance, U.S. patent application Ser. No. 357,632 (or EP-A2-0 296 590) and U.S. patent application Ser. No. 221,092 (or EP-A2-0 300 481).
In the optical card recording/reproducing apparatus, two guide rods 13 are arranged in parallel in a casing 10 having a card inserting port 11, thereby constructing a guiding mechanism 12. A holder 2 is supported to the guiding mechanism 12 so that it can reciprocate. In correspondence to the portions below a holder moving path, an optical head 6 is arranged on the card inserting side and a card feeding mechanism 5 is arranged on the rear side, respectively.
As shown in FIG. 20, bearings 20 are provided on both sides of the holder 2, thereby supporting the holder 2 to the guide rods 13. A card holding mechanism 21 is provided below the lower surface of the holder 2. A height position of the card holding mechanism 21 is set to a position of the card inserting port 11 of the casing 10.
As shown in FIGS. 22 and 26, the card holding mechanism 21 is constructed in the following manner. Flanges 22 which inwardly project are formed in the lower portions of opposite side walls of the holder 2, thereby supporting both side portions of the optical card 1. A card pressing plate 23 whose both side portions face the flanges 22 is arranged between the side walls of the holder 2. Pressurizing means 24 whose pressing force can be adjusted is provided for the card pressing plate 23. A portion 23a on the card inserting port side of the card pressing plate 23 is slightly bent so as to provide a gap between the portion 23a and the flange 22. On the other hand, an opposite side edge portion of the card pressing plate 23 is loosely inserted into concave portions formed in the holder 2. Guide rollers 41, 42, and 43 are provided on the flanges 22.
The pressurizing means 24 comprises springs 24a and 24b and a lever 25. The springs 24a are arranged between both side portions of the card pressing plate 23 and a part of the holder 2 and generate a relatively weak pressing force. The other springs 24b are arranged between the lever 25 and a part of the holder 2 and generate a pressing force which is stronger than that of the springs 24a. One end of the lever 25 is pivotally supported to the rear side of the holder 2. A pressing projected portion 26 which is come into contact with the central portion of the card pressing plate 23 is formed on the lower surface of the lever 25. In the other edge portion of the lever 25, an arm 25a extends toward the side and passes through a notched portion of the holder 2 and, further, extends downwardly. Through the arm 25a, the lever 25 is pushed up by a cam, a solenoid, or other operating mechanism 24c against the spring force of the springs 24b.
Returning to FIGS. 20 and 21, a sensor 31 and a card loading/ejecting mechanism 3 are arranged on the inside of the card inserting port 11. The sensor 31 detects the inserted optical card 1. In response to the result of the detection of the sensor 31, the card loading/ejecting mechanism 3 automatically loads and ejects out the optical card 1 into/from the card holding mechanism 21 of the holder 2.
The card loading/ejecting mechanism 3 is located below the holder 2. A pair of right and left loading cams 33 are attached to a rotary shaft 32 which is rotatably supported to the casing 10. The rotary shaft 32 is driven by a loading motor 37 through a reducing mechanism comprising a pulley 36a and a belt 36b. The loading cam 33 is an almost semicircular cam made of a rubber material. When a flat cam surface 33a of the loading cam 33 is located horizontally over the rotary shaft 32, the cam surface 33a approaches the lower surface of the holder 2 in a contactless manner. When the loading cams 33 are rotated by the loading motor 37, circular cam surfaces 33b of the cams 33 are come into contact with the optical card 1 and convey the card 1 to a predetermined position of the card holding portion 22. Then, the flat cam surfaces 33a again face the holder 2 and the motor 37 stops. The card 1 is ejected out by rotating the cams 33 in the direction opposite to that in the loading operation.
A guide rod 27 is arranged on the rear side of the holder 2 in the direction perpendicular to the moving direction of the holder 2. The guide rod 27 movably supports a slide member 28 and couples the slide member 28 to the card feeding mechanism 5 in the following manner.
The card feeding mechanism 5 is constructed in the following manner. Two shafts 51 are rotatably supported to a fixed frame 50 in the casing 10. Pulleys 52 and 53 are fixedly attached to both shafts 51. An endless belt 54 is wound and reeved between the pulleys 52 and 53. A coupling pin 55 is vertically attached at a proper position of the endless belt 54. The pin 55 is rotatably coupled with the slide member 28. A pulley 56 is fixed to the lower portion of the shaft 51. A rotational force of a drive motor 58 which can rotate in a single direction is transferred to the pulley 56 through transfer means 57 such as a belt or the like. A rotary encoder 59 is attached to the other shaft 51. A center of gravity G of the card holder 2 and a driving center point P of the feeding mechanism 5 are aligned on the same line which is parallel with the moving direction of the holder 2 when it is seen from the flat surface (also from the side surface) in the case where the holder 2 is moved from the card inserting port side toward the rear direction. Such an arrangement is realized by setting the center of the coupling pin 55 of the slide member 28 to a position on a card feeding direction line passing through the center of gravity G of the holder 2.
The optical head 6 is supported to a lead screw 60 which is rotatably supported in the direction perpendicular to the moving direction of the holder 2 and to a fixed guide rod 61. The lead screw 60 is driven by a head feeding motor 62 which can forwardly and reversely rotate. Therefore, when the motor 62 operates, the optical head 6 is guided by the guide rod 61 and lead screw 60 and is moved in the direction perpendicular to the feeding direction of the optical card 1 by the rotation of the lead screw 60. Thus, the optical head 6 accesses a predetermined information recorded on a recording track of the optical card 1. A head feeding mechanism 7 is constructed by the lead screw 60, guide rod 61, and motor 62.
The operation of the optical card recording/reproducing apparatus with the above construction will now be described. In a card insertion waiting state, the holder 2 is located near the card inserting port 11. In this state, when the optical card 1 is inserted from the card inserting port 11 and the card insertion is detected by the sensor 31, the card loading/ejecting mechanism 3 operates. Thus, the inserted optical card 1 is automatically carried to the card holding mechanism 21.
Subsequently, when the drive motor 58 of the card feeding mechanism 5 operates and the endless belt 54 is moved, the coupling pin 55 formed on the belt 54 draws and moves the holder 2 along the guide shafts 13 through the slide member 28. The holder 2 is reciprocated by the continuous rotation in the single direction of the drive motor 58. While the holder 2 is being returned toward the card inserting port 11, the information recording portion 16 of the optical card 1 is relatively moved with respect to the optical head 6, thereby recording/reproducing information. When the holder 2 is returned to the first position on the side of the inserting port 11, the head feeding motor 62 operates and the optical head 6 accesses the track through the lead screw 60 and guide rod 61. The card feeding operation is again repeated in a manner similar to the above.
FIG. 27 shows an example of a construction of the optical head 6. The head 6 comprises: a light projection optical system 71 to irradiate the light onto the optical card 1; and a light reception optical system 81 to receive the reflected lights from the optical card 1.
The light projection optical system 71 includes: a semiconductor laser 73, a collimating lens 74, a warping prism 75, a diffraction grating 76, a reflecting mirror 77, and an objective lens 78. The spreading light emitted from the semiconductor laser 73 is transformed into the parallel beam having an elliptic cross section by the collimating lens 74. After the parallel beam was warped to the beam having an almost circular cross section by the warping prism 75, it is divided into three light beams by the diffraction grating 76. The three light beams are led in the direction of the optical card 1 by the reflecting mirror 77 and images are formed onto the optical card 1 by an objective lens 78. As shown in FIG. 28, a light spot SPa due to a 0th-order diffracted light is formed on the information recorded or recording track 17. On the other hand, light spots SPb and SPc due to positive and negative primary diffracted lights are formed on the track guides 18 on both sides of the track 17, respectively.
In addition to the objective lens 78 and the reflecting mirror 77, the light reception optical system 81 includes: condenser lenses 82 and 83; a half-mirror 84; and photo detectors 85 and 86. The reflected lights of the light spots SPa, SPb, and SPc are converged by the condenser lenses 82 and 83 through the objective lens 78 and reflecting mirror 77. The converged light is separated by the half-mirror 84. The separated lights are projected to the photo detectors 85 and 86, respectively.
In the above optical system, in order to accurately form the image of the light spot SPa onto the information recording portion 16 of the optical card 1, it is necessary to control the distance between the optical card 1 and the objective lens 78 (focusing control). On the other hand, in order to accurately form the image of the light spot SPa to the position of the information recorded or recording track 17 in the information recording portion 16, it is necessary to control the position of the objective lens 78 (tracking control). A focusing error signal and a tracking error signal which are used for the focusing control and tracking control are produced from light detection signals of the photo detectors 85 and 86. On the basis of the focusing error signal, a focusing servo mechanism controls the distance of the objective lens 78 to the optical card 1. On the basis of the tracking error signal, a tracking servo mechanism controls the position in the lateral direction of the objective lens 78 so that the light spots SPb and SPc are located on the track guides 18.
In the recording mode, in a state in which the automatic focusing and tracking controls were executed, the semiconductor laser 73 is driven by high power pulses which were modulated on the basis of data to be recorded while moving the optical card 1 in the direction along the track guides 18, thereby causing a thermal irreversible change on the information recording portion 16 of the optical card 1 by the 0th-order diffracted light. In this manner, a pit train is produced and information is recorded.
On the other hand, in the reproducing mode, in a similar state in which the automatic focusing and tracking controls were executed, the pit train is scanned by the 0th-order diffracted light while moving the optical card 1 in the direction of the track guide 18, thereby detecting the reflected lights by the photo detector 86. The recorded information on the optical card 1 is read out on the basis of an output signal of the photo detector 86.
FIG. 29 shows a circuit block diagram of the optical card recording/reproducing apparatus with the above construction. The optical head 6 is controlled by focusing control circuit 45 and a tracking control circuit 46 and is electrically connected to a system controller 48 through a signal processor 47 for processing the light detection signal. The focusing control circuit 45 and tracking control circuit 46 are controlled by the system controller 48. The card loading/ejecting mechanism 3 and the head feeding mechanism 7 are electrically connected to the system controller 48. The card feeding mechanism 5 is also electrically connected to the system controller 48 through a card feeding control circuit 44. The operation in each section of the mechanisms in the recording or reproducing mode is controlled by the system controller 48. The system controller 48 is connected to an external terminal device 70 through an external interface 49.
In the optical card recording/reproducing apparatus with the above construction, the focusing error signal and tracking error signal, as fundamental signals for the focusing and tracking servo controls, are formed on the basis of the light emitted from the semiconductor laser 73 as a light source. Therefore, when the semiconductor laser 73 is intermittently driven by a large amount of power in the information recording mode, the fundamental signals are largely fluctuated, so that focusing and tracking control errors occur. To avoid such errors, when the semiconductor laser 73 is intermittently driven to output a large output, it is necessary to interrupt the focusing and tracking controls and to keep the position of the objective lens 78 to the position just before the driving by a high power. Consequently, such control becomes very complicated.
When the recorded information is reproduced, a pit train of the pits 19 on the track 17 is scanned by the light spot SPa of an almost same size as that of the pit 19 and a change in light amount of the reflected light is detected by the photo detector 86. Therefore, if a vibration occurs in association with the conveyance of the optical card 1, the light spot SPa is deviated from the pit 19, so that an S/N ratio of the light detection signal deteriorates. Particularly, in the optical card recording/reproducing apparatus, the vibration is larger than that in the optical disk drive apparatus or the like. If the recording or reproducing speed of information is intended to increase, the vibration also increases due to such a high speed operation. Therefore, it is difficult to realize the high recording/reproducing speed.
Further, when the recorded information is reproduced, the semiconductor laser 73 is used in a state in which its power is reduced to a lower limit level enough to stably oscillate. However, even in the case of such a low level, there is a problem such that energy densities of the light spots SPa to SPc are still high and the pits 19 and track guides 18 on the optical card 1 are deteriorated by the repetitive reproducing operations, so that the light detection signal level is decreased.
FIG. 30 is a constructional diagram showing another example of a general construction of an optical head which is assembled in the optical card recording/reproducing apparatus.
In the diagram, the optical head comprises: a semiconductor laser 91 as a light source to project a light to the optical card 1 side; a photo detector 100 which is constructed by various kinds of photo sensitive elements for receiving the reflected lights from the optical card 1 and outputting electric signals corresponding to amounts of lights detected; and an optical system for leading the light emitted from the semiconductor laser 91 to the optical card 1 and for leading the reflected lights from the optical card 1 to the photo detector 100. The optical system comprises: a collimating lens 92; a deflecting beam splitter 93; an objective lens 94; and a condenser lens 95.
In the above construction, the light emitted from the semiconductor laser 91 is transmitted through the collimating lens 92 and deflecting beam splitter 93 and reaches the objective lens 94. Then, it is converged by the objective lens 94 and is irradiated onto the optical card 1. In a manner opposite to the above, the reflected lights from the optical card 1 pass through the objective lens 94 and are deflected by the deflecting beam splitter 93 and are converged by the condenser lens 95 and are input to the photo detector 100. The photo detector 100 has reproduction signal photo sensitive elements, photo sensitive elements for focusing control, and a photo sensitive element for tracking control. Electric signals corresponding to detected light amounts are output from the photo sensitive elements, respectively.
A focusing control mechanism in the optical head will now be described with reference to FIG. 31.
In the diagram, the lights reflected by the optical card 1 in the light emitted from the semiconductor laser 91 pass through the condenser lens 95 and are detected by two photo sensitive elements 101a and 101b for focusing control included in the photo detector 100. Electric signals from the photo sensitive elements 101a and 101b for focusing control are respectively amplified by amplifiers 105a and 105b and are given to a differential amplifier 106 to amplify the difference between the amplified outputs of the amplifiers 105a and 105b. A drive mechanism 109 of the objective lens 94 is driven by a focusing control circuit 107 on the basis of a differential output F of the differential amplifier 106.
In the above construction, when the optical card 1 exists at a position indicated by A and a relative distance between the optical card 1 and the objective lens 94 is set to the optimum distance, the reflected lights from the optical card 1 pass through the objective lens 94 and condenser lens 95 and enter the photo sensitive elements 101a and 101b for focusing control with an equal light amount, so that the differential output F of the differential amplifier 106 is set to zero.
On the other hand, if the optical card 1 exists at a position shown by B or C, the reflected lights are deviated to either one of the photo sensitive elements 101a and 101b and form an image, so that the differential amplifier 106 outputs the negative or positive differential output F.
FIG. 32 is a graph showing the relation between the relative distance between the objective lens 94 and the optical card 1 and the differential output F in the above construction. When the optical card 1 exists at the position A, the difference output F is set to zero. When the optical card 1 exists at the position of B or C, the differential output F has a negative or positive value corresponding to the relative distance. Such a case corresponds to a state in which the focusing control is not correctly executed. When the signal having a negative or positive value is output as a differential output F, in order to set the differential output F to zero, the focusing control circuit 107 actuates the drive mechanism 109 so as to adjust the position of the objective lens 94, that is, to execute what is called a focusing control.
However, when the focusing control as mentioned above is executed, there are the following problems.
FIGS. 33a and 33b are diagrams showing the corresponding relations among the optical card 1, an irradiation light spot SP (corresponding to a detection light spot on the photo sensitive elements for focusing control) which is projected onto the optical card 1, and the photo sensitive elements 101a and 101b for focusing control. As shown in FIG. 33a, when the irradiation light spot SP exists at a normal position in the direction perpendicular to the track guides 18 of the optical card 1, the irradiation light spot SP includes two track guides 18 in its region. The differential output F in this case is obtained as shown by a solid line in the graph of FIG. 32. On the other hand, if the light spot SP exists at a position which is deviated from the normal position as shown in FIG. 33b, the light spot SP irradiates three track guides 18. In such a case, a reflected light amount 18 decreases by the amount of one track guide (that is, the reflectance of the track guide is smaller than those of the other portions as mentioned above), so that the differential output F decreases as shown by a broken line in FIG. 32. As mentioned above, there is a problem such that when the differential output F fluctuates, the focusing control cannot be accurately executed.
As a method of solving the above problems, for instance, there is considered to provide a holding mechanism for always keeping the irradiating position of the irradiation light spot SP to the optical card 1 to the normal position or to provide a correction processing circuit of the differential signal F for the focusing control circuit 107. However, such methods are not practical because a construction of the apparatus becomes complicated and it takes a long processing time.
As another optical card recording/reproducing apparatus, there has been known an apparatus having a construction in which photo sensitive elements for recording/reproducing, photo sensitive elements for focusing control, and a photo sensitive element for tracking control are respectively arranged on one flat surface as the photo detector 100. FIGS. 34a and 34b are diagrams showing the corresponding relations among recording/reproducing photo sensitive elements 102, the photo sensitive elements 101a and 101b for focusing control, and a photo sensitive element 103 for tracking control of the photo detector 100, an irradiation light spot SP1 on the optical card 1 (an incident light spot on the photo detector 100 is also the same as the irradiation light spot SP1), and the optical card 1. In the photo detector 100, the photo sensitive elements 101a and 101b for focusing control are arranged in the lower portion, one of the recording/reproducing photo sensitive elements 102 is arranged in the upper portion, the photo sensitive element 103 for tracking control is arranged in the further upper portion, and the other recording/reproducing photo sensitive element 102 is arranged in the further upper portion ("upper" and "lower" denote "upper" and "lower" in FIGS. 34a and 34b).
However, when the focusing control is executed in the photo detector 100 in which the photo sensitive elements 101a, 101b, 102, and 103 are arranged on one flat surface, there are the following problems.
That is, as shown in FIG. 34a, when the major axis direction of the elliptic detection light spot SP1 which is obtained in the photo detector 100 coincides with the arranging direction of the photo sensitive elements 101a to 103, the focusing control is correctly executed. However, as shown in FIG. 34b, if the major axis of the detection light spot SP1 is inclined and deviated from the normal position, even if the focusing state is normal (the position shown by A in FIG. 31), a large amount of incident light from the detection light spot SP1 is detected by either one of the photo sensitive elements 101a and 101b for focusing control. Such a state is not regarded as a correct focusing state, so that the focusing control cannot be correctly executed. Such a situation in which the detection light spot SP1 is inclined and deviated from the normal position occurs in the case where the irradiation light spot SP1 was obliquely irradiated onto the optical card 1 or where the detection light spot SP1 by the reflected light is formed onto the photo detector 100 in a twisted state due to a fluctuation of the optical system.
As a method of solving the above problems, for instance, there is considered to provide an adjusting mechanism for adjusting so that the major axis direction of the detection light spot SP1 coincides with the arranging direction of the photo sensitive elements 101a to 103. However, such a method is not practical because a construction of the apparatus becomes complicated and it takes a long processing time.
FIG. 35 shows the detecting operation of further another photo detector. That is, FIG. 35 is a diagram for explaining a detected light amount of the recording/reproducing photo sensitive elements of the photo detector 100 in the case where the optical card 1 was scanned by the irradiation light spot (corresponding to the detection light spot). When the optical card 1 is moved in the direction of a blank arrow, the irradiation light spot relatively moves to the positions indicated by SP21, SP22, and SP23. When a light spot SP21 is projected to the position where the pit 19 exists in association with the movement of the light spot, the reflected light amount becomes minimum and the detected light amount is also set to the minimum value k.sub.1. On the other hand, when a light spot SP23 is projected to the position where no pit 19 exists, the reflected light amount is set to the maximum value k.sub.2. A reproduction signal is formed on the basis of such a detected light amount.
However, in the above construction, there is a problem such that the detected light amount is not accurately obtained in correspondence to the presence or absence of the pit 19 and a reproduction signal of the correct information cannot be formed.
That is, for instance, if the irradiation light spot SP22 exists at the just intermediate position of the two pits 19, both side portions of the irradiation light spot SP22 are projected to the pits 19 locating on both sides, respectively. Thus, an intermediate light amount k.sub.3 between the minimum light amount k.sub.1 and the maximum light amount k.sub.2 is detected. Such an intermediate light amount k.sub.3 becomes an obstacle upon formation of the reproduction signal.